According to a new study published in the Proceedings of the National Academy of Sciences journal, painting roofs white or covering them with plants could help offset global warming.
The study finds that these type of measures are effective in offsetting or counteracting the effects of city growth and global warming due to greenhouse gases, but researchers warn there needs to be careful planning for them to work correctly and effectively.
The study, led by Matei Georgescu of Arizona State University and collages Philip Morefield, Britta Bierwagen and Christopher Weaver all of the U.S. Environmental Protection Agency, examined how these technologies fare across different geographies and climates of the U.S.
“Each can completely offset the warming due to urban expansion and can even offset the warming due to greenhouse gas emissions,” explains Georgescu. He says cool and green roofs can become an important way to deal with rising temperatures, especially as more Americans live in urban areas that are warmed by asphalt roads and tar roofs.
“This is the first time all of these approaches have been examined across various climates and geographies,” said Georgescu. “We looked at each adaptation strategy and their impacts across all seasons, and we quantified consequences that extend to hydrology (rainfall), climate and energy. We found geography matters,” he added.
For example, the effectiveness of a cool roof, painting the roof white to reflect the sun and reduce indoor temperatures during the summer, in Florida versus using a cool roof in California.
What works in California’s Central Valley does not necessarily provide the same benefits to other regions of the U.S., like Florida, Georgescu said.
“There are trade-offs that need to be considered,” Georgescu says, adding: “We don’t yet know enough about the various trade-offs.” His study, funded by the National Science Foundation.
“The study is a step in the right direction and is consistent with other studies that suggest that cool roofs can offset localized urban heat island impacts,” says Mark Jacobson, an environmental engineering professor at Stanford University. He says, however, it does not show the global impact.
All in all, researchers confirm “White roofs win based on the purely economic factors we included, and black roofs should be phased out,” author Arthur Rosenfeld said. He added, white and green roofs do “a good job at cooling the building and cooling the air in the city, but white roofs are three times more effective at countering climate change than green roofs.”
Although, he added green roofs, where produce can be grown, offer a whole different level of benefits such as storm-water management and urban gardening.
Overall, the researchers suggest that judicious planning and design choices should be considered in trying to counteract rising temperatures caused by urban sprawl and greenhouse gasses.
White Roofs Are Better for the Environment Than Green Roofs
According to a study by researchers at the Lawrence Berkeley National Laboratory in California and the Nanyang Technological University in Singapore, having a white colored roof is actually better for the environment and cheaper than having a green roof covered with plants.
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